Multi-range cross defrosting heat pump system and humidity control system

ABSTRACT

The present invention provides an air-condition heat pump system and two-stage defrosting control method for continuous operation under an environment temperature range from 20 degree to negative 40 degree Celsius or lower. The heat pump system employs different defrosting methods under different temperature and humidity conditions. A ventilation and humidity control system is also provided for implementing the cross defrosting heat pump system within an indoor dimension.

FIELD Field of the Invention

The present invention relates to a multi-range air-condition heat pump, more particularly to a multi-range air-condition heat pump capable of uninterrupted operation. The present invention can be applied on residential, agriculture, commercial transportation, and industrial purposes. More particularly, the present invention can be used for air-conditioning, refrigeration.

BACKGROUND OF THE INVENTION

Current available heat pump requires different types of compressors for different range of working environment temperature, therefore, the user may need to install multiple air-conditioning systems such as a combination of a heat pump and a gas heater for different range of working temperature. One of the reasons is the low efficiency of the heat pump under low working temperature, another reason is the need for interrupting operation due to the frost conditions on evaporators.

The current defrosting methods such as electrical defrost system and reverse-circulation defrost system require the heat pump to stop operation while defrosting. Therefore, it is one objective of the present invention to provide an air-condition heat pump capable of uninterrupted operation during system defrosting process.

Another objective of the present invention is to provide the most efficient control methods for cross defrosting heat pump system under different temperature and humidity conditions; most heat pumps require the heat energy from other source to maintain the heating efficiency while the present invention defrosts with the heat energy absorbed from the environment and the heat energy generated by the compressor.

Current compressors have very low efficiency under low temperature range, the current two-stage compressors utilize two compression strokes to increase system efficiency, however, the current two-stage compressors can not operate under different temperature range, in other words, the two-stage compressor can not operate under the environment that does not require pressure boosting; therefore it is another objective of the present invention to provide a multi-stage pressure boosting heat pump system capable of adjusting the level of pressure boosting in order to operate under a wide range of working environment temperature.

Current ventilation and humidity control systems can not fully utilize the heat energy in the indoor air exhaust, therefore it is yet another objective to provide a ventilation and humidity control system to combine with the multi-range cross defrosting heat pump systems of the present invention. The ventilation and humidity control system recycles the heat energy from the indoor exhaust and adjusts the ventilation rate according to the humidity percentage. For the human comfort in most indoor space, the ventilation rate required is directly proportional to the humidity percentage, the ventilation and humidity control system of the present invention raises the ventilation rate by automatically adjusting the defrosting duration, since the multi-range cross defrosting heat pump system of the present invention requires more defrosting time when the humidity percentage of the working environment is high.

In general, current heat pump system has very limited range of working temperatures due to the limitation and the operation efficiency of the compressor; however, in many circumstances, the environment temperature may vary from negative 40 degree to 20 degree Celsius, therefore it is main objective of the present invention to provide a multi-range cross defrosting heat pump capable of operating under a wide range of working environment temperature at high efficiency.

SUMMARY OF THE INVENTION

1. It is a primary object of the present invention to provide a multi-range cross defrosting heat pump system capable of operating under various range of temperature.

2. It is a second object of the present invention to provide a multi-range cross defrosting heat pump system capable of uninterrupted continuous operation during defrosting process.

3. It is another object of the present invention to provide the most efficient defrosting control method for the multi-range cross defrosting heat pump system which is capable of defrosting with the heat energy absorbed from the environment and the heat energy generated from the compressor, therefore minimizing the energy required for defrosting process.

4. It is yet another object of the present invention to provide a ventilation and humidity control system that can combine and fully utilize the multi-range cross defrosting heat pump of the present invention.

BREIF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 1I are the illustrative diagrams of the cross reverse defrosting heat pump system. The control logic table of cross reverse defrosting heat pump system is provided as a reference to FIG. 1A to FIG. 1E

FIG. 1F is an exemplary construction scheme of the cross reverse defrosting heat pump system utilizing rotary valves.

FIG. 1H is an exemplary construction scheme of the cross reverse defrosting heat pump system utilizing more than two evaporators.

FIG. 1I is another possible modified construction scheme based on the cross reverse defrosting heat pump system.

FIG. 2A to FIG. 2F are the illustrative diagrams of the cross defrosting heat pump system with defrost condensers. The control logic table of cross defrosting heat pump system is provided as a reference to FIG. 2A to FIG. 2E.

FIG. 3A to FIG. 3E are the illustrative diagrams of the cross defrosting heat pump system with separate refrigerant circulation and defrost condensers. The control logic table of cross defrosting heat pump with separate circulation system is provided as a reference to FIG. 3A to FIG. 3E.

FIG. 4 is an illustrative diagram of the cross electric defrosting heat pump system. The control logic table of cross electric defrosting heat pump system is provided as reference to FIG. 4.

FIG. 5A to FIG. 5E are illustrative diagrams of the ventilation and humidity control system combined with the cross defrosting heat pump system of the present invention. The control logic table of self-ventilation and humidity control system for cross defrosting heat pump is provided as a reference to FIG. 5A to FIG. 5E.

FIG. 6A to FIG. 6G are the illustrative diagrams of the cross anti-freeze-fluid defrosting heat pump system. The control logic table of cross anti-freeze-fluid-defrosting heat pump system is provided as a reference for FIG. 6A to FIG. 6E.

FIG. 1G, FIG. 3F, FIG. 2F, FIG. 6F are the exemplary construction schemes of the multi-range cross defrosting heat pump systems capable of operation under 20 degree Celsius to negative 40 degree Celsius.

FIG. 1J, FIG. 2G, FIG. 5F, FIG. 6H are the exemplary construction schemes of the multi-range cross defrosting heat pump system with four sets of operating evaporators.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1A, the cross reverse defrosting heat pump system comprising the following basic components: main compressor 101, main condenser 102, first evaporator 121, second evaporator 122, main expansion valve 103, first upper-flow control valve 131, second upper-flow control valve 132, first lower-flow control valve 171, second lower-flow control valve 172, first reverse-flow control valve 151, second reverse-flow control valve 152, first expansion valve 141, second expansion valve 142, first one-way valve 161, second one-way valve 162, first venting fan(not shown), second venting fan(not shown), separate insulation means(not shown) for each evaporator, and the logic control circuit(not shown).

When the outdoor temperature is above 12 degree Celsius, first evaporator 121 and second evaporator 122 should be capable of functioning without defrosting. When the outdoor temperature is between 5 to 12 degree Celsius, the logic control circuit employs first stage defrosting method. When the outdoor temperature is lower than 5 degree, the logic control circuit employs second stage defrosting method. It should be noted that each threshold temperature is estimated under general humidity condition.

As shown in FIG. 1A, when first evaporator 121 and second evaporator 122 are operating, first upper-flow control valve 131 and first lower-flow control valve 171 and second upper-flow control valve 132 and second lower-flow control valve 172 are open. First reverse-flow control valve 151 and second reverse-flow control valve 152 are closed. The refrigerant in said two evaporators absorbs heat from the ambient air flow and is pressurized in main compressor 101, and then the refrigerant flows through main condenser 102 to release heat. Main expansion valve 103 is used to control the refrigerant pressure difference between main condenser 102 and said two evaporators.

When the first stage defrosting method is employed, the cross reverse defrosting heat pump system operates with a working schedule which is depending on the outdoor temperature and the humidity. An exemplary working schedule is provided as follow, after first evaporator 121 and second evaporator 122 have operated for 5 minutes, first evaporator 121 starts defrosting by the ambient air flow while first upper-flow control valve 131 and first lower-flow control valve 171 are closed to stop refrigerant flow for 5 minutes as shown in FIG. 1B. After the defrosting process of first evaporator 121 has ended, first evaporator 121 ad second evaporator 122 operate together for another 5 minutes, then second evaporator 122 starts defrosting by the ambient air flow while second upper-flow control valve 132 and second lower-flow control valve 172 are closed to stop refrigerant flow for 5 minutes as shown in FIG. 1C, thus completed one working cycle. During each defrosting process with the first stage defrosting method, the functioning evaporator will still operate to absorb heat. First venting fan and second venting fan are operating all the time for the first stage defrosting method.

A working schedule is provided for the second stage defrosting method. After first evaporator 121 and second evaporator 122 operate for 10 minutes, first evaporator 121 starts cross reverse defrosting process for 5 minutes while second evaporator 122 continue to operate. Next, first evaporator 121 and second evaporator 122 operate together for another 5 minutes, and then second evaporator 122 starts cross reverse defrosting process, thus completed one defrosting cycle.

As shown in FIG. 1D, when first evaporator 121 starts cross reverse defrosting process, first upper-flow control valve 131 and first lower-flow control valve 171 are closed, first reverse-flow control valve 151 is open so that the pressurized refrigerant from main compressor 101 flows directly into first evaporator 121 and starts heating to melt the ice on first evaporator 121 while first venting fan stops running to prevent heat from escaping into open air. The refrigerant in first evaporator 121 exits through first expansion valve 141 and first one-way valve 161 into the input side of second evaporator 122, thus first evaporator 121 is defrosted by the heat energy absorbed from second evaporator 122 and generated from main compressor 101. Second one-way valve 162 is used to prevent the refrigerant in first evaporator 121 from entering the discharge side of second evaporator 122.

As shown in FIG. 1E, when second evaporator 122 starts cross reverse defrosting process, second upper-flow control valve 132 and second lower-flow control valve 172 are closed, second reverse-flow control valve 152 is open so that the pressurized refrigerant from main compressor 101 flows directly into second evaporator 122 and starts heating to melt the ice on second evaporator 122 while second venting fan stops running to prevent heat from escaping into open air. The refrigerant in second evaporator 122 exits through second expansion valve 142 and second one-way valve 162 into the input side of first evaporator 121, thus second evaporator 122 is defrosted by the heat energy absorbed from first evaporator 121 and generated from main compressor 101. First one-way valve 161 is used to prevent the refrigerant in second evaporator 122 from entering the discharge side of first evaporator 121.

When the first stage defrosting method is employed, if evaporator temperature sensor detects that the temperature of the defrosting evaporator has risen over approximately 3 degree, the logic control circuit will reset the working schedule to the next step. For example, if second evaporator 122 has melt all the ice at 18 minute of the working schedule, the logic control circuit will be reset to 20 minute of the working schedule and both evaporators start operating to absorb heat.

The cross reverse defrosting heat pump system can further comprises additional evaporators as shown in FIG. 1H. When each evaporator is defrosting with first stage defrosting method, that evaporator stops operating by closing its associated upper-flow control valve and lower-flow control valve, and its associated venting fan is running to defrost with the ambient air flow.

When each evaporator is defrosting with second stage defrosting method, its associated upper-flow control valve and lower-flow control valve are closed, and its reverse-flow control valve is open to provide direct passage for the pressurized refrigerant into that evaporator. Its associated venting fan stops operating to conserve the heat within the heat insulated space of that evaporator. The second stage defrosting method utilizes the heat absorbed from the functioning evaporators and the heat generated from main compressor 101 to melt the ice on the evaporator that is defrosting. An exemplary working schedule is provide for the cross reverse defrosting heat pump with 3 evaporators; all evaporators are operating at full capacity for 5 minutes, then first evaporator 121 defrosts for 5 minutes, then second defrosts for 5 minutes, then third evaporator defrosts for 5 minutes, thus completed one working cycle.

For easier maintenance, most control valves can be combined into one single rotary valve or other multi-port control valve means. An control valve construction scheme of the cross reverse defrosting heat pump system with rotary is provided in FIG. 1F, where first reverse-flow control valve 151 and first upper-flow control valve 131 are replaced with first rotary upper-flow control valve 131 capable of same functions, first lower-flow control valve 171 and first one-way valve 161 can be replaced with first rotary lower-flow control valve 171 capable of same functions. Another construction scheme is provided in FIG. 1I, where the pressurized refrigerant enters the defrosting evaporator from the discharge side of the defrosting evaporator during the cross reverse defrosting process. Many other construction schemes and control valve means are possible to perform the same task based on the present invention and should be considered within the scoop of the present invention.

Referring now to FIG. 2A, this is another cross defrosting heat pump system. The logic control circuit and first venting fan and second venting fan and the heat insulation means for each evaporator are not shown for clarification purpose.

As shown in FIG. 2A, if defrosting is not necessary, first defrost control valve 214 and second defrost control valve 213 are closed to stop refrigerant flowing into first defrost condenser 205 and second defrost condenser 206, the refrigerant is pressurized in compressor 201 and flowed through main condenser 202 to release heat, then the refrigerant flows through expansion valve 207 into first evaporator 203 and second evaporator 204. Then the refrigerant is evaporated and drawn back to compressor 201.

As shown in FIG. 2B, when first evaporator 203 is defrosting with the first stage defrosting method, first evaporator control valve 212 is closed to stop refrigerant flow into first evaporator 203, and then first venting fan is running at full capacity to defrost second evaporator 204 with the ambient air flow.

As shown in FIG. 2C, when second evaporator 204 is defrosting with the first stage defrosting method, second evaporator control valve 211 is closed to stop refrigerant flow into second evaporator 204, and then second venting fan is running at full capacity to defrost second evaporator 204 with the ambient air flow.

As shown in FIG. 2D, when first evaporator 203 is defrosting with the second stage defrosting method, first evaporator control valve 212 is closed to stop refrigerant flowing into first evaporator 203, first defrost control valve 214 is open to allow pressurized refrigerant into first defrost condenser 205 to provide heat for defrosting first evaporator 203, then the refrigerant in first defrost condenser 205 flows through its associated flow regulator 221 into the intake side of second evaporator 204. First venting fan stops running to prevent heat from escaping out of the heat insulated space of first evaporator 203.

As shown in FIG. 2E, when second evaporator 204 is defrosting with the second stage defrosting method, second evaporator control valve 211 is closed to stop refrigerant flowing into second evaporator 204, second defrost control valve 213 is open to allow pressurized refrigerant into second defrost condenser 206 to provide heat for defrosting second evaporator 204, then the refrigerant in second defrost condenser 206 flows through its associated flow regulator 222 into the intake side of first evaporator 203. Second venting fan stops running to prevent heat from escaping out of the heat insulated space of second evaporator 204

During the second stage defrosting, the defrosting evaporator is heated up by the heat absorbed by the functioning evaporator and generated by the compressor.

FIG. 3A shows a cross defrosting heat pump with separate circulation system, this system comprising: first compressor 311, first condenser 312, first expansion valve 313, first evaporator 314, first defrost condenser 316, second compressor 321, second condenser 322, second expansion valve 323, second evaporator 324, second defrost condenser 326, third compressor 331, third condenser 332, third expansion valve 333, third evaporator 334, first venting fan(not shown), second venting fan(not shown), third venting fan(not shown), first defrost control valve 315, second defrost control valve 325, third defrost control valve 335, first defrost-condenser expansion valve 317, second defrost-condenser expansion valve 327, third defrost-condenser expansion valve 337, separate heat insulation means(not shown) for each evaporator, and the logic control circuit(not shown).

First evaporator 314 is in direct contact with third evaporator 334, second evaporator 324 is in direct contact with second evaporator 324, and third evaporator 334 is in direct contact with first evaporator 314.

When the environment temperature is above approximately 12 degree Celsius, all three evaporators are operating and all three defrost control valves are closed as shown in FIG. 3A. When the environment temperature is between 5 to 12 degree Celsius, and the frost is accumulating on the evaporators during operation, the first stage defrosting method is employed. When the environment is below 5 degree Celsius, the second stage defrosting method is employed.

A working schedule is provided for the first stage defrosting method, all evaporators operate for 5 minutes, and then first compressor 311 stops operating and uses the ambient air flow to defrost for 5 minutes while second evaporator 324 and third evaporator 334 continues to operate. Next, second compressor 321 stops operating and uses the ambient air flow to defrost for 5 minutes while first evaporator 314 and third evaporator 334 continue to operate. Next, third compressor 331 stops operating and uses the ambient air flow to defrost for 5 minutes while first evaporator 314 and second evaporator 324 continue to operate, thus completed one working cycle. All venting fan are operating at full capacity when the first stage defrosting method is employed.

As shown in the working schedule and the control valve table, when the second stage defrosting method is employed, all compressors operate for 5 minutes, and then first compressor 311 stops operating while third defrost control valve 335 is open to heat up third defrost condenser 336 to melt the ice on first evaporator 314 for 5 minutes as shown in FIG. 3B, next, second compressor 321 stops operating while first defrost control valve 315 is open to heat up first defrost condenser 316 to melt the ice on second evaporator 324 for 5 minutes as shown in FIG. 3C, next third compressor 331 stops operating while second defrost control valve 325 is open to heat up second defrost condenser 326 to melt the ice on third evaporator 334 as shown in FIG. 3D, thus completed one working cycle. During the defrosting process of each evaporator, the other two operating compressors and evaporators continue to operate for both heating and defrosting purpose. Each venting fan stops operating to conserve heat energy within its associated heat insulated space when its associated evaporator is defrosting with the second stage defrosting method. Additional fans can be installed on each defrost condenser to increase the efficiency of the defrosting process

The cross defrosting heat pump with separate circulation system would generally require at least three equivalent compressors to provide a heating system efficient enough for continuous operation, however the overall efficiency can not match other cross defrosting system as described in other embodiments of the present invention.

Referring now to FIG. 4, this is another cross defrosting heat pump system based on the embodiment described in FIG. 2A. The logic control circuit and first venting fan and second venting fan and the heat insulation means for each evaporator are not shown for clarification purpose.

As shown in FIG. 4, if defrosting is not necessary, first electric heating element 481 and second electric heating element 482 are not conducted, the refrigerant is pressurized in compressor 401 and flowed through main condenser 402 to release heat, then the refrigerant flows through expansion valve 407 into first evaporator 403 and second evaporator 404. Then the refrigerant is evaporated and drawn back to compressor 401.

When first evaporator 403 is defrosting with the first stage defrosting method, first evaporator control valve 412 is closed to stop refrigerant flow into first evaporator 403, and then first venting fan is running at full capacity to defrost first evaporator 403 with the ambient air flow.

When second evaporator 404 is defrosting with the first stage defrosting method, second evaporator control valve 411 is closed to stop refrigerant flow into second evaporator 404, and then second venting fan is running at full capacity to defrost second evaporator 404 with the ambient air flow.

When first evaporator 403 is defrosting with the second stage defrosting method, first evaporator control valve 412 is closed to stop refrigerant flowing into first evaporator 493, first electric heating element 481 is conducted to generate heat to defrost first evaporator 403. First venting fan stops running to prevent heat from escaping out of the heat insulated space of first evaporator 203.

When second evaporator 404 is defrosting with the second stage defrosting method, second evaporator control valve 4111 is closed to stop refrigerant flowing into second evaporator 404, second electric heating element 482 is conducted to generate heat to defrost second evaporator 404. Second venting fan stops running to prevent heat from escaping out of the heat insulated space of second evaporator 404

FIG. 5A shows the cross defrosting heat pump with self-ventilation and humidity control system. The system comprising: main compressor 591, main condenser 502, expansion valve 503, first evaporator 511, second evaporator 512, first control valve 521, second control valve 522, first venting fan 541, second venting fan 542, first temperature sensor 531, second temperature sensor 532, outdoor temperature sensor 599, outdoor-air-intake duct 590, cold-air-exit duct 592, first outdoor-air-intake control valve 571, second outdoor-air-intake control valve 572, first indoor-air-intake control valve 561, second indoor-air intake-control valve 562, first indoor-air-intake fan 551, second indoor-air-intake fan 552, heat insulation means for each evaporators, and the control logic circuit.

The self-ventilation and humidity control system as described in this embodiment can be combined with all other cross defrosting heat pump as described in other embodiment of the present invention. First evaporator 5111 and second evaporator 512 can be disposed in indoor space with separate heat insulation means. This system is also capable of the first stage defrosting method and the second stage defrosting method as described in other embodiments of the present invention.

As shown in FIG. 5A, when the outdoor temperature is above 12 degree Celsius under general humidity condition, first evaporator 511 and second evaporator 512 are capable of operation without defrosting, first outdoor-air-intake control valve 571 and second outdoor-air-intake control valve 572 are open to provide passage of ambient air flow through first evaporator 511 and second evaporator 512. First indoor-air-intake control valve 561 and second indoor-air-intake control valve 562 are closed to conserve indoor temperature. First venting fan 541 and second venting fan 542 are running to vent the cold air to open air through cold-air-exit duct 592.

As shown in FIG. 5B and FIG. 5C, when the outdoor temperature is between 5 to 12 degree Celsius and the frost starts to accumulate on both evaporators during operation, the control logic circuit will employ the first stage defrosting method. A working schedule of the first stage defrosting method is provided: first evaporator 511 and second evaporator 512 operate for 10 minutes, and then first evaporator 511 defrosts with ambient air flow for 5 minutes as shown in FIG. 5B, and then both first evaporator 511 and second evaporator 512 operate for another 5 minutes, and then second evaporator 512 defrosts with ambient flow for 5 minutes as shown in FIG. 5C, thus completed one working cycle. First venting fan 541 and second venting fan 542 are operating at full capacity when the first stage defrosting method is employed. During defrosting of each evaporator, the defrosting evaporator stops the refrigerant flow by closing its associated control valve, and the frost on the defrosting evaporator melts by absorbing the heat from the ambient air flow through outdoor-air-intake duct 590.

As shown in FIG. 5D and FIG. 5E, when the outdoor temperature is below 5 degree Celsius and the first stage defrosting method is not sufficient to provide enough heat to melt the frost on first evaporator 511 and second evaporator 512, the control logic will employ the second stage defrosting method. A working schedule of the second stage defrosting method is provided: first evaporator 511 and second evaporator 512 operate for 10 minutes, and then first evaporator 511 defrosts with indoor air flow for 5 minutes, and then both first evaporator 511 and second evaporator 512 operate for 5 minutes, and then second evaporator 512 defrosts with indoor air flow for 5 minutes, thus completed one working cycle.

When first evaporator 5111 is defrosting with the second stage defrosting method as shown in FIG. 5D, first evaporator 511 stops the refrigerant flow by closing first control valve 521, first outdoor-air-intake control valve 571 is closed and first indoor-air-intake control valve 561 is open so that the frost on first evaporator 511 melts by absorbing the heat from the indoor air flow. First indoor-air-intake fan 551 is operating to control the indoor air flow into the heat insulated space of first evaporator 511. First venting fan 541 is operating at the speed based on the temperature difference measured by outdoor temperature sensor 599 and first temperature sensor 531. The control logic circuit compares the outdoor temperature and the temperature within the insulated space associated with first evaporator 511, when the temperature measured by first temperature sensor 531 is higher than the outdoor temperature, first venting fan 541 will run slowly or stop running to prevent the heat from escaping into the open air through cold-air-exit duct 592. During the defrosting process of first evaporator 5111, second evaporator 5112 continues to operate to absorb heat from the ambient air flow so that main condenser 502 can maintain the temperature within the indoor space.

More complex control logic can be applied to the speed of first indoor-air-intake fan 551 and first venting fan 541 for higher defrosting efficiency, while the basic concept is to fully utilize the heat energy of the indoor air flow to defrost first evaporator 511. In the case when the temperature measured by first temperature sensor 531 is almost the same as the temperature measured by the indoor temperature sensor, first indoor-air-intake fan 551 will slowly decrease its speed during the defrosting process of first evaporator 511. In the case when first evaporator 511 has finished its defrosting process and the first control valve 521 is open to allow the refrigerant flow but first temperature sensor 531 measured a higher temperature than the outdoor temperature, first venting fan 541 will not start operation until second temperature sensor 532 measured a lower temperature than the outdoor temperature so that the remaining heat can be fully utilized.

When second evaporator 512 is defrosting with the second stage defrosting method as shown in FIG. 5E, second evaporator 512 stops the refrigerant flow by closing second control valve 522, second outdoor-air-intake control valve 572 is closed and second indoor-air-intake control valve 562 is open so that the frost on second evaporator 512 melts by absorbing the heat from the indoor air flow. Second indoor-air-intake fan 552 is operating to control the indoor air flow into the heat insulated space of second evaporator 512. Second venting fan 542 is operating at the speed based on the temperature difference measured by outdoor temperature sensor 599 and second temperature sensor 532. At the beginning of the defrosting process, second venting fan 542 is running slowly to vent the cold air, allowing the indoor air to flow into the heat insulated space of second evaporator 512. The control logic circuit compares the outdoor temperature and the temperature within the insulated space associated with second evaporator 512, when the temperature measured by second temperature sensor 532 is higher than the outdoor temperature, second venting fan 542 will run slowly or stop running to prevent the heat from escaping into the open air through cold-air-exit duct 592. During the defrosting process of the second evaporator 512, first evaporator 511 continues to operate to absorb heat from the ambient air flow so that main condenser 5@2 can maintain the temperature within the indoor space.

More complex control logic can be applied to the speed of second indoor-air-intake fan 552 and second venting fan 542 for higher defrosting efficiency, while the basic concept is to fully utilize the heat energy of the indoor air flow to defrost second evaporator 5112. In the case when the temperature measured by second temperature sensor 532 is almost the same as the temperature measured by the indoor temperature sensor, second indoor-air-intake fan 552 will slowly decrease its speed during the defrosting process of second evaporator 512. In the case when second evaporator 512 has finished its defrosting process, and second control valve 522 is open to allow the refrigerant flow but second temperature sensor 532 measured a higher temperature than the outdoor temperature, second venting fan 542 will not start operation until second temperature sensor 532 measured a lower temperature than the outdoor temperature so that the remaining heat can be fully utilized.

During the second stage defrosting of each evaporator, each indoor-air-intake fan is drawing the indoor air into its associated evaporator, and the outdoor air is drawing into the indoor space through other ventilation duct for ventilation purpose, or an indoor ventilation fan can co-work with this system and draws outdoor air into the indoor space during the second stage defrosting of each evaporator.

Under general conditions, when a defrosting process sensor is installed to detect if the evaporator requires further defrosting, the system can automatically adjust the ventilating time. Because the indoor space generally requires more ventilating time if the humidity level is high, while the frosting condition of the evaporators also depends on the humidity, therefore, if there is a low level of humidity, the frost on the evaporators only need to defrost for a short time and reset to the next step of the working schedule, while the ventilating time is depending on the duration of the defrosting process. During the second stage defrosting of each evaporator, its associated indoor-air-intake control valve is open for ventilation purpose.

In most cases, first venting fan 541 and second venting fan 542 only operate when its associated temperature sensor reads a lower temperature reading than the outdoor temperature in order to fully utilize the remaining heat energy before releasing to open air. However, there are different operation modes requiring different control logics.

First operation mode is the scheduled defrosting mode, where each evaporator takes turn to defrost on a fixed time schedule. This operation mode can further employ a defrosting process sensor means to detect if the evaporator has melted all the ice on the evaporator, if no further defrosting is required, the control logic reset it to the next step of the working schedule. The defrosting process sensor means can be a pressure or temperature sensor on the defrosting evaporator.

Second operation mode is the automatic defrost mode, where the evaporators are running under an environment condition that will take a very long time before the defrosting process is needed. A defrosting process sensor is used to determine when the system requires defrosting. If the system requires defrosting, the system will change into the schedule defrosting mode until no further defrosting is required.

Third operation mode is the forced-ventilation mode, where each indoor-air-intake control valve is open and its associated indoor-air-intake fan is running to draw in the indoor air for ventilation purpose during the operation of its associated evaporator.

Under third operation mode, the outdoor air flow is mixed with the indoor air flow through each indoor-air-intake control valve. By controlling the temperature of this mixed air flow, the time required for each defrosting process can be greatly reduced, or under some conditions, the system can continue to operate without defrosting. In the case when the outdoor temperature is between 5 to 12 degree Celsius, the temperature of the mixed air flow can be raised to 12 degree so that the system can greatly increase the operation time of both first evaporator 511 and second evaporator 5I2 before the first stage defrosting is required. If the temperature of the mixed air flow is raised to above 12 degree, the system can operate without defrosting. If the outdoor temperature is below 5 degree, raising the temperature of the mixed air flow can also greatly increase the operation time of both first evaporator 511 and second evaporator 512 before the second stage defrosting is required.

The temperature of the mixed air flow can be controlled by each indoor-air-intake control valve, the operation speed of each venting fan and indoor-air-intake fan, and there are other ways of controlling the temperature of the mixed air flow, but it is not discussed here beyond necessary.

It should be noted that the control logic of the venting fans is different when the system is operating under the forced-ventilation mode, where each venting fan is not operating at the speed based on the temperature difference between the outdoor temperature and the temperature within the heat insulated space associated with each evaporator. The venting fans are operating at the speed based on the ventilation rate required or the temperature of the mixed air flow required.

This ventilation system can combine with other cross defrosting heat pump systems as mentioned in other embodiments of the present invention. A combination of the cross reverse defrosting heat pump and the self-ventilation and humidity control system is most preferable for large heat pump systems. It is also possible to utilize separate refrigerant circulation as shown in FIG. 3A, where the refrigerant in each evaporator is pressurized by separate compressors.

As shown in FIG. 6A, if the system is working under the environment temperature that does not require defrosting, first fluid pump 631 and second fluid pump 632 are not operating so that refrigerant-to-fluid heat exchanger 603 does not dissipate any heat energy, the refrigerant is pressurized in main compressor 601 and flows through main condenser 602 to release heat, then the refrigerant flows through expansion valve 60, into first anti-freeze-fluid-defrost evaporator 611 and second anti-freeze-fluid-defrost evaporator 612. Then the refrigerant is evaporated and drawn back to compressor 601.

As shown in FIG. 6B, when first anti-freeze-fluid-defrost evaporator 611 is defrosting with the first stage defrosting method, first control valve 621 is closed to stop refrigerant flow in first anti-freeze-fluid-defrost evaporator 611, and then first venting fan is running at full capacity to defrost first evaporator 6111 with the ambient air flow.

As shown in FIG. 6C, when second anti-freeze-fluid-defrost evaporator 612 is defrosting with the first stage defrosting method, second control valve 622 is closed to stop refrigerant flow in second anti-freeze-fluid-defrost evaporator 612, and then second venting fan is running at full capacity to defrost second anti-freeze-fluid-defrost evaporator 612 with the ambient air flow.

As shown in FIG. 6D, when first anti-freeze-fluid-defrost evaporator 611 is defrosting with the second stage defrosting method, first control valve 621 is closed to stop refrigerant flow in first anti-freeze-fluid-defrost evaporator 611, first fluid pump 631 is pumping to generate the anti-freeze fluid flow which transfers the heat from refrigerant-to-fluid heat exchanger 603 to first anti-freeze-fluid-defrost evaporator 611, therefore, the system can defrost with the heat energy generated from main compressor 601 and the heat energy absorbed by the other operating anti-freeze-fluid-defrost evaporator. First venting fan decreases speed or stops running to prevent heat from escaping out of the separated space of first anti-freeze-fluid-defrost evaporator 611.

As shown in FIG. 6E, when second anti-freeze-fluid-defrost evaporator 612 is defrosting with the second stage defrosting method, second control valve 622 is closed to stop refrigerant flow in second anti-freeze-fluid-defrost evaporator 612, second fluid pump 632 is pumping to generate the anti-freeze fluid flow which transfers the heat from refrigerant-to-fluid heat exchanger 603 to second anti-freeze-fluid-defrost evaporator 612, therefore, the system can defrost with the heat energy generated from main compressor 601 and the heat energy absorbed by the other operating anti-freeze-fluid-defrost evaporator. Second venting fan decreases speed or stops running to prevent heat from escaping out of the separated space of second anti-freeze-fluid-defrost evaporator 612.

During the second stage defrosting, each defrosting anti-freeze-fluid-defrost evaporator is heated up by the heat energy absorbed by the functioning anti-freeze-fluid-defrost evaporator and the heat energy generated by main compressor.

Another objective of the present invention is to provide a heat pump system capable of operation under low temperature range with a high temperature range compressor or a medium temperature range compressor. A pressure boosting jet pump is employed in the cross reverse defrosting heat pump as shown in FIG. 1G. When the environment temperature drops to about 0 degree Celsius, the pressure boosting control valve is open, and the pressure boosting jet pump is enabled so that the intake refrigerant pressure of the compressor is increased and the compressor can operate at the optimum load. The pressure boosting jet pump utilizes the discharge refrigerant pressure of the compressor to increase the intake refrigerant pressure of the compressor. When the pressure boosting jet pump is used with a typical refrigerant such as R22, the high temperature range compressor can still operate under negative 40 degree Celsius. If one stage pressure boosting is not sufficient to maintain the intake refrigerant pressure of the compressor for optimum load, multiple stage of pressure boosting can be applied. Same concept can apply to all other embodiments mentioned in the present invention. A pressure boosting control valve is used to adjust the amount of the refrigerant flowing into the pressure boosting jet pump.

The pressure boosting jet pump can also be substituted with a rotary pump or a mechanical turbo-charged pump which also utilizes the discharge refrigerant pressure of the compressor to sustain the intake refrigerant pressure of the compressor for optimum compressor load. The pressure boosting control valve can be a servo valve or a solenoid valve. A one-way by-pass passage may be required for uses with the rotary pump or the mechanical turbo-charged pump.

FIG. 1G, FIG. 3F, FIG. 2F, FIG. 6F are the exemplary construction schemes of the wide temperature range heat pump systems capable of operation under 20 degree Celsius to negative 40 degree Celsius.

FIG. 1J, FIG. 2G, FIG. 5F, FIG. 6H are the exemplary construction schemes of the multi-range cross defrosting heat pump systems with four sets of operating evaporators.

It should be understood that the threshold temperatures for initiating each stage of defrosting are different for other regions in the world, where the humidity and frosting condition are the main factor deciding which defrosting method to apply at different temperature range. All evaporators First evaporator Second evaporator First evaporator Second evaporator Label Component Name operating 1^(st) Stage Defrosting 1^(st) Stage Defrosting 2^(nd) stage defrosting 2^(nd) Stage Defrosting Control Logic Table of Cross Reverse Defrosting Heat Pump System 102 Main condenser Operating Operating Operating Operating Operating 121 First evaporator Operating Defrosting with Operating Cross Reverse Operating outdoor air flow Defrosting (no refrigerant flow) 122 Second evaporator Operating Operating Defrosting with Operating Cross Reverse outdoor air flow Defrosting (no refrigerant flow) 151 First reverse-flow Closed Closed Closed Open Closed control valve 152 Second reverse-flow Closed Closed Closed Closed Open control valve 131 First upper-flow Open Closed Open Closed Open control valve 171 First lower-flow Open No effect Open Closed Open control valve 132 Second upper-flow Open Open Closed Open Closed control valve 172 Second lower-flow Open Open No effect Open Closed control valve First venting fan Operating at Operating at Operating at Decreasing speed Operating at full speed full speed full speed full speed Second venting fan Operating at Operating at Operating at Operating at Decreasing speed full speed full speed full speed full speed Control Logic Table of Cross Defrosting Heat Pump System 202 Main condenser Operating Operating Operating Operating Operating 203 First evaporator Operating Defrosting with Operating Defrosting by Operating outdoor air flow first defrost (no refrigerant flow) condenser 204 Second evaporator Operating Operating Defrosting with Operating Defrosting by outdoor air flow second defrost (no refrigerant flow) condenser 214 First defrost Closed Closed Closed Open Closed control valve 213 Second defrost Closed Closed Closed Closed Open control valve 212 First evaporator Open Closed Open Closed Open control valve 205 First defrost No refrigerant flow No refrigerant flow No refrigerant flow Operating No refrigerant flow condenser 211 Second evaporator Open Open Closed Open Closed control valve 206 Second defrost No refrigerant flow No refrigerant flow No refrigerant flow No refrigerant flow Operating condenser First venting fan Operating at Operating at Operating at Decreasing speed Operating at full speed full speed full speed full speed Second venting fan Operating at Operating at Operating at Operating at Decreasing speed full speed full speed full speed full speed

Control Logic Table of Cross Defrosting Heat Pump with Separate Circulation System Part 1 All First evaporator Second evaporator Third evaporator evaporators 1^(st) Stage 1^(st) Stage 1^(st) stage Label Component Name operating Defrosting Defrosting defrosting 311 First compressor Operating Resting Operating Operating 321 Second compressor Operating Operating Resting Operating 331 Third compressor Operating Operating Operating Resting 312 First condenser Operating Resting Operating Operating 322 Second condenser Operating Operating Resting Operating 332 Third condenser Operating Operating Operating Resting 314 First evaporator Operating Defrosting with Operating Operating outdoor air flow 324 Second evaporator Operating Operating Defrosting with Operating outdoor air flow 334 Third evaporator Operating Operating Operating Defrosting with outdoor air flow 315 First defrost Closed Closed Closed Closed control valve 325 Second defrost Closed Closed Closed Closed control valve 335 Third Closed Closed Closed Closed defrost control valve 316 First defrost condenser Resting Resting Operating Resting 326 Second defrost Resting Resting Resting Operating condenser 336 Third defrost condenser Resting Operating Resting Resting First venting fan Operating at Operating at Operating at Operating at full speed full speed full speed full speed Second venting fan Operating at Operating at full Operating at full Operating at full speed speed speed full speed Third venting fan Operating at Operating at full Operating at full Operating at full full speed speed speed speed

Control Logic Table of Cross Defrosting Heat Pump with Separate Circulation System Part 2 First Second Third evaporator evaporator evaporator Component 2^(nd) Stage 2^(nd) Stage 2^(nd) Stage Label Name Defrosting Defrosting Defrosting 311 First compressor Resting Operating Operating 321 Second compressor Operating Resting Operating 331 Third compressor Operating Operating Resting 312 First condenser Resting Operating Operating 322 Second condenser Operating Resting Operating 332 Third condenser Operating Operating Resting 314 First evaporator Defrosting Operating Operating by third defrost condenser 324 Second evaporator Operating Defrosting Operating by first defrost condenser 334 Third evaporator Operating Operating Defrosting by second defrost condenser 315 First defrost Closed Open Closed control valve 325 Second defrost Closed Closed Open control valve 335 Third defrost Open Closed Closed control valve 316 First defrost Resting Operating Resting condenser 326 Second defrost Resting Resting Operating condenser 336 Third defrost Operating Resting Resting condenser First venting Decreasing Operating at Operating at fan speed full speed full speed Second venting Operating at Decreasing Operating at fan full speed speed full speed Third venting Operating at Operating at Decreasing fan full speed full speed speed

Control Logic Table of Cross Electric Defrosting Heat Pump System All evaporators First evaporator Second evaporator First evaporator Second evaporator Label Component Name operating 1^(st) Stage Defrosting 1^(st) Stage Defrosting 2^(nd) stage defrosting 2^(nd) Stage Defrosting 402 Main condenser Operating Operating Operating Operating Operating 403 First evaporator Operating Defrosting with Operating Defrosting by Operating outdoor air flow first electric (no refrigerant flow) heating element 404 Second evaporator Operating Operating Defrosting with Operating Defrosting by outdoor air flow second electric (no refrigerant flow) heating element 412 First evaporator Open Closed Open Closed Open control valve 481 First electric Not conducted Not conducted Not conducted Conducted Not conducted heating element 411 Second evaporator Open Open Closed Open Closed control valve 482 Second electric Not conducted Not conducted Not conducted Not conducted Conducted heating element First venting fan Operating at Operating at Operating at Decreasing speed Operating at full speed full speed full speed full speed Second venting fan Operating at Operating at Operating at Operating at Decreasing speed full speed full speed full speed full speed

Control Logic Table of Self-ventilation and Humidity Control System for Cross Defrosting Heat Pump Part 1 First Second All evaporator evaporator Component evaporators 1^(st) Stage 1^(st) Stage Label Name operating Defrosting Defrosting 502 Main Operating Operating Operating condenser 512 First Operating Defrosting Operating evaporator with outdoor air flow 511 Second Operating Operating Defrosting evaporator with outdoor air flow 521 First Open Closed Open control valve 522 Second Open Open Closed control valve 561 First Closed Closed Closed indoor- air-intake control valve 562 Second Closed Closed Closed indoor- air-intake control valve 571 First Open Open Open outdoor- air-intake control valve 572 Second Open Open Open outdoor- air-intake control valve 551 First Resting Resting Resting indoor- air-intake fan 552 Second Resting Resting Resting indoor- air-intake Fan 541 First Operating Operating Operating venting fan at full at full at full speed speed speed 542 Second Operating Operating Operating venting fan at full at full at full speed speed speed

Control Logic Table of Self-ventilation and Humidity Control System for Cross Defrosting Heat Pump Part 2 First Second evaporator evaporator Component 2^(nd) Stage 2^(nd) Stage Forced- Label Name Defrosting Defrosting ventilation 502 Main Operating Operating Operating condenser 512 First Defrosting Operating Operating evaporator with indoor with mixed air flow air flow 511 Second Operating Defrosting Operating evaporator with indoor with mixed air flow air flow 521 First Closed Open Open control valve 522 Second Open Closed Open control valve 561 First Open Closed Open with indoor- controlled air-intake air flow rate control valve 562 Second Closed Open Open with indoor- controlled air-intake air flow rate control valve 571 First Closed Open Open with outdoor- controlled air-intake air flow rate control valve 572 Second Open Closed Open with outdoor- controlled air-intake air flow rate control valve 551 First Operating Resting Operating indoor- to provide to provide air-intake Indoor air Indoor air fan flow flow 552 Second Resting Operating Operating indoor- to provide to provide air-intake Indoor air Indoor air Fan flow flow 541 First Resting Operating Operating at venting at full controlled fan speed speed 542 Second Operating Resting Operating at venting at full controlled fan speed speed

Control Logic Table of Cross Anti-Freeze-Fluid-Defrosting Heat Pump System All evaporators First evaporator Second evaporator First evaporator Second evaporator Label Component Name operating 1^(st) Stage Defrosting 1^(st) Stage Defrosting 2^(nd) stage defrosting 2^(nd) Stage Defrosting 602 Main condenser Operating Operating Operating Operating Operating 603 Refrigerant-to-fluid Operating Operating Operating Operating Operating heat changer 611 First anti-freeze Operating Defrosting with Operating Defrosting by Operating fluid-defrost outdoor air flow heated anti-freeze evaporator (no refrigerant flow) fluid 612 Second anti-freeze Operating Operating Defrosting with Operating Defrosting by fluid-defrost outdoor air flow heated anti-freeze evaporator (no refrigerant flow) fluid 621 First control valve Open Closed Open Closed Open 631 First fluid pump No pumping No pumping No pumping Pumping No pumping 622 Second control valve Open Open Closed Open Closed 632 Second fluid pump No pumping No pumping No pumping No pumping Pumping First venting fan Operating at Operating at Operating at Decreasing speed Operating at full speed full speed full speed full speed Second venting fan Operating at Operating at Operating at Operating at Decreasing speed full speed full speed full speed full speed 

1. A cross reverses defrosting heat pump system comprising: a) main compressor for pressurizing the refrigerant, b) main condenser following main compressor for heating purpose, c) main expansion valve following main condenser, d) first evaporator and second evaporator receiving the refrigerant through main expansion valve, e) first upper-flow control valve for controlling the refrigerant flow into the intake side of first evaporator, first lower-flow control valve for controlling the refrigerant flow out of the discharge side of first evaporator into the intake side of main compressor, g) second upper-flow control valve for controlling the refrigerant flow into the intake side of second evaporator, second lower-flow control valve for controlling the refrigerant flow out of the discharge side of second evaporator into the intake side of main compressor, h) first reverse-flow control valve for controlling the refrigerant flow from main compressor directly into the intake side of first evaporator, i) second reverse-flow control valve for controlling the refrigerant flow from main compressor directly into the intake side of second evaporator, j) first one-way valve and first expansion valve associated with the refrigerant delivery pipe between the discharge side of first evaporator and intake side of second evaporator, k) second one-way valve and second expansion valve associated with the refrigerant delivery pipe between the discharge side of second evaporator and intake side of first evaporator, l) separate heat insulation means for first evaporator and second evaporator, m) first venting fan for venting the air out of the heat insulated space associated with first evaporator, n) second venting fan for venting the air out of the heat insulated space associated with second evaporator, o) the logic control circuit for controlling the two stage defrosting operation; the system is capable of two stage defrosting operation, where first evaporator and second evaporator operate together until the defrosting process is required; when the defrosting process is required and the outdoor temperature is enough for defrosting with ambient air flow, first evaporator and second evaporator takes turn to defrost while the operating evaporator continues to operate and absorb the heat energy require for the heating purpose; when first evaporator is defrosting with the ambient air flow, first upper-flow control valve is closed and first lower-flow control valve is closed to stop the refrigerant flow from main expansion valve, and first venting fan is operating at full capacity to increase the ambient air flow through first evaporator; when second evaporator is defrosting with the ambient air flow, second upper-flow control is closed and second lower-flow control valve is closed to stop the refrigerant flow from main expansion valve, and second venting fan is operating at full capacity to increase the ambient air flow through second evaporator; when first evaporator is defrosting with the second stage defrosting method, first upper-flow control valve is closed and first lower-flow control valve is closed to stop the refrigerant flow from main expansion valve, first reverse-flow control valve is open to provide passage for the pressurized refrigerant from main compressor into first evaporator for melting the frost on first evaporator, and the first venting fan stops operating to prevent the heat from escaping into open air, while the pressurized refrigerant heats up first evaporator and flows into the refrigerant delivery pipe into the intake side of second evaporator; when second evaporator is defrosting with the second stage defrosting method, second upper-flow control valve is closed and second lower-flow control valve is closed to stop the refrigerant flow from main expansion valve, second reverse-flow control valve is open to provide passage for the pressurized refrigerant from main compressor into second evaporator for melting the frost on second evaporator, and the second venting fan stops operating to prevent the heat from escaping into open air, while the pressurized refrigerant heats up second evaporator and flows into the refrigerant delivery pipe into the intake side of first evaporator.
 2. A cross defrosting heat pump system comprising: a) One compressor 201 for pumping and pressurizing the refrigerant into a main condenser 202, b) First evaporator 203 and second evaporator 204 following said main condenser 202, c) An expansion valve 207 for regulating the pressure drop between said main condenser 202 and said two evaporators 203 204, d) First evaporator control valve 212 associated with said first evaporator 203 for stopping the flow of the refrigerant during defrosting process of said first evaporator 203, e) Second evaporator control valve 211 associated with said second evaporator 204 for stopping the flow of the refrigerant during defrosting process of said second evaporator 204, f) First defrost condenser 205 connecting and receiving the refrigerant from the discharge port of said compressor 201, and the refrigerant exiting into said second evaporator 204, g) First defrost control valve 214 for admitting the refrigerant flow into said first defrost condenser 205 during the defrosting process of said first evaporator 203, i) Second defrost condenser 206 connecting and receiving the refrigerant from the discharge port of said compressor 201, and the refrigerant exiting into said first evaporator 203, j) Second defrost control valve 213 for admitting the refrigerant flow into said defrost condenser 206 during the defrosting process of said second evaporator 204; k) First flow regulator 221 connected between said first defrost condenser 205 and said second evaporator 204 for controlling the refrigerant flow and the heat energy required for the defrosting process, and second flow regulator 222 connected between second defrost condenser 206 and said first evaporator 203 for controlling the refrigerant flow and the heat energy required for the defrosting process; l) Heat transferring means for said two defrost condensers 205 206 transferring the heat onto said two evaporators 203 204 respectively during defrosting process; wherein when the defrosting process is not necessary, both said first control valve 213 and said second control valve 214 remain closed to stop refrigerant flow into first defrost condenser and second defrost condenser; when first evaporator 203 is defrosting with the first stage defrosting method, first evaporator control valve 212 is closed to stop refrigerant flow into first evaporator 203, and then first venting fan is running at full capacity to defrost first evaporator 203 with the ambient air flow; when second evaporator 204 is defrosting with the first stage defrosting method, second evaporator control valve 211 is closed to stop refrigerant flow into second evaporator 204, and then second venting fan is running at full capacity to defrost second evaporator 204 with the ambient air flow; when first evaporator 203 is defrosting with the second stage defrosting method, first evaporator control valve 212 is closed to stop refrigerant flowing into first evaporator 203, first defrost control valve 214 is open to allow pressurized refrigerant into first defrost condenser 205 to provide heat for defrosting first evaporator 203, then the refrigerant in first defrost condenser 205 flows through its associated flow regulator 221 into the intake side of second evaporator 204, first venting fan stops running to prevent heat from escaping out of the heat insulated space of first evaporator 203; when second evaporator 204 is defrosting with the second stage defrosting method, second evaporator control valve 211 is closed to stop refrigerant flowing into second evaporator 204, second defrost control valve 213 is open to allow pressurized refrigerant into second defrost condenser 206 to provide heat for defrosting second evaporator 204, then the refrigerant in second defrost condenser 206 flows through its associated flow regulator 222 into the intake side of first evaporator 203, second venting fan stops running to prevent heat from escaping out of the heat insulated space of first evaporator 204; during the second stage defrosting, the defrosting evaporator is heated up by the heat absorbed by the functioning evaporator and generated by the compressor so that the heat pump system does not require additional energy from other source to defrost.
 3. A cross defrosting heat pump with separate refrigerant circulation comprising: a) at least three separate refrigerant circulation system, b) first refrigerant circulation system consists of first compressor for pressurizing the refrigerant, first condenser connecting to the discharge side of first compressor, first expansion valve following first condenser, first evaporator receiving the refrigerant from first condenser through first expansion valve, first defrost condenser connecting its intake side to the discharge side of first compressor and its discharge side to first expansion valve, first defrost control valve for controlling the refrigerant flow into first defrost condenser, first one-way valve for stopping the refrigerant flow from first condenser into first defrost condenser, first venting fan for controlling air flow through first evaporator, c) second refrigerant circulation system consists of second compressor for pressurizing the refrigerant, second condenser connecting to the discharge side of second compressor, second expansion valve following second condenser, second evaporator receiving the refrigerant from second condenser through second expansion valve, second defrost condenser connecting its intake side to the discharge side of second compressor and its discharge side to second expansion valve, second defrost control valve for controlling the refrigerant flow into second defrost condenser, second one-way valve for stopping the refrigerant flow from second condenser into second defrost condenser, second venting fan for controlling air flow through second evaporator, d) third refrigerant circulation system consists of third compressor for pressurizing the refrigerant, third condenser connecting to the discharge side of third compressor, third expansion valve following third condenser, third evaporator receiving the refrigerant from third condenser through third expansion valve, third defrost condenser connecting its intake side to the discharge side of third compressor and its discharge side to third expansion valve, third defrost control valve for controlling the refrigerant flow into third defrost condenser, third one-way valve for stopping the refrigerant flow from third condenser into third defrost condenser, third venting fan for controlling air flow through third evaporator, d) first evaporator is in direct contact with third evaporator, second evaporator is in direct contact with second evaporator, third evaporator is in direct contact with first evaporator, e) separate heat insulation means for each evaporator; when all three evaporators are operating, all venting fan are operating to provide the ambient air flow through each evaporator, each defrost control valve is closed to stop the refrigerant flow through each defrost condenser; when the system is defrosting with the first stage defrosting method, the defrosting evaporator stops its refrigerant flow by turning off its associated compressor, and its associated venting fan is running at full capacity to defrost with the ambient air flow; when first evaporator is defrosting with the second stage defrosting method, first compressor stops operating, and first venting fan stops operating to prevent the heat from escaping into open air, third defrost control valve is open to allow the refrigerant flowing through third defrost condenser which heats up first evaporator and melts the frost on first evaporator, when second evaporator is defrosting with the second stage defrosting method, second compressor stops operating, and second venting fan stops operating to prevent the heat from escaping into open air, first defrost control valve is open to allow the refrigerant flowing through first defrost condenser which heats up second evaporator and melts the frost on second evaporator; when third evaporator is defrosting with the second stage defrosting method, third compressor stops operating, and third venting fan stops operating to prevent the heat from escaping into open air, second defrost control valve is open to allow the refrigerant flowing through second defrost condenser which heats up third evaporator and melts the frost on third evaporator.
 4. An electric cross-defrosting heat pump system comprising: a) One compressor for pumping and pressurizing the refrigerant into a main condenser, b) First evaporator and second evaporator following said main condenser, c) An expansion valve for regulating the pressure drop between said main condenser and said first evaporator and said second evaporator, d) First control valve associated with said first evaporator for stopping the flow of the refrigerant during defrosting process of said first evaporator, e) Second control valve associated with said second evaporator for stopping the flow of the refrigerant during defrosting process of said second evaporator, f) First electric heating element for defrosting said first evaporator during the defrosting process of said first evaporator, g) Second electric heating element for defrosting said second evaporator during the defrosting process of said second evaporator, h) frost sensor means and the logic control circuit for detecting the frost condition and controlling the defrosting process; when the defrosting process is not necessary, both said first control valve and said second control valve remain closed; when first evaporator is defrosting with the first stage defrosting method, first evaporator control valve is closed to stop refrigerant flow into first evaporator, and then first venting fan is running at full capacity to defrost first evaporator with the ambient air flow; when second evaporator is defrosting with the first stage defrosting method, second evaporator control valve is closed to stop refrigerant flow into second evaporator, and then second venting fan is running at full capacity to defrost second evaporator with the ambient air flow; when first evaporator is defrosting with the second stage defrosting method, first evaporator control valve is closed to stop refrigerant flowing into first evaporator, first electric heating element is conducted to generate heat to defrost first evaporator, first venting fan stops running to prevent heat from escaping out of the heat insulated space of first evaporator; when second evaporator is defrosting with the second stage defrosting method, second evaporator control valve is closed to stop refrigerant flowing into second evaporator, second electric heating element is conducted to generate heat to defrost second evaporator, second venting fan stops running to prevent heat from escaping out of the heat insulated space of second evaporator.
 5. A cross defrosting heat pump with self-ventilation and humidity control system comprising: a) main compressor for pressurizing the refrigerant, b) main condenser following said main compressor, c) main expansion valve following said main condenser, d) first evaporator following said main expansion valve and connecting its discharge side to said main compressor, e) second evaporator following said main expansion valve and connecting its discharge side to said main compressor, f) first control valve associated with said first evaporator for stopping the refrigerant flow when said first evaporator is defrosting, g) second control valve associated with said second evaporator for stopping the refrigerant flow when said second evaporator is defrosting, h) heat insulation means for each said evaporator, i) indoor temperature sensor, j) first temperature sensor associated with the heat insulated space associated with said first evaporator, k) second temperature sensor associated with the heat insulated space associated with said second evaporator, l) outdoor temperature sensor, m) first indoor-air intake control valve and first indoor-air-intake fan for controlling the indoor air flow into the heat insulated space associated with said first evaporator, n) second indoor-air-intake control valve and second indoor-air-intake fan for controlling the indoor air flow into the heat insulated space associated with said second evaporator, o) outdoor-air-intake duct for providing air flow passage from outdoor into the heat insulated space of each evaporator, p) cold-air-exit duct for providing air flow passage from the heat insulated space of each evaporator to outdoor, p) first venting fan for controlling and venting the air flow from the heat insulated space of said first evaporator to said cold-air-exit duct, q) second venting fan for controlling and venting the air flow from the heat insulated space of said second evaporator to said cold-air-exit duct, r) the control logics circuit; when first evaporator is defrosting with the first stage defrosting method, first evaporator stops the refrigerant flow by closing first control valve, first outdoor-air-intake control is open and first venting fan is operating at full speed to defrost first evaporator with the ambient air flow; when second evaporator is defrosting with the second stage defrosting method, second evaporator stops the refrigerant flow by closing second control valve, second outdoor-air-intake is open and second venting fan is operating at full speed to defrost second evaporator with the ambient air flow; during the first stage defrosting method, the defrosting evaporator stops operating, other evaporator continues to operate for heating and defrosting purpose; When first evaporator is defrosting with the second stage defrosting method, first evaporator stops the refrigerant flow by closing first control valve, first outdoor-air-intake control valve is closed and first indoor-air-intake control valve is open so that the frost on first evaporator melts by absorbing the heat from the indoor air flow; first indoor-air-intake fan is operating to control the indoor air flow into the heat insulated space of first evaporator; first venting fan is operating at the speed based on the temperature difference measured by outdoor temperature sensor and first temperature sensor; the control logic circuit compares the outdoor temperature and the temperature within the heat insulated space associated with first evaporator, when the temperature measured by first temperature sensor is higher than the outdoor temperature, first venting fan will run slowly or stop running to prevent the heat from escaping into the open air through cold-air-exit duct; during the defrosting process of first evaporator, second evaporator continues to operate to absorb heat from the ambient air flow so that main condenser can maintain the temperature within the indoor space; When second evaporator is defrosting with the second stage defrosting method, second evaporator stops the refrigerant flow by closing second control valve, second outdoor-air-intake control valve is closed and second indoor-air-intake control valve is open so that the frost on second evaporator melts by absorbing the heat from the indoor air flow; second indoor-air-intake fan is operating to control the indoor air flow into the heat insulated space of second evaporator; second venting fan is operating at the speed based on the temperature difference measured by outdoor temperature sensor and second temperature sensor; at the beginning of the defrosting process, second venting fan is running slowly to vent the cold air, allowing the indoor air to flow into the heat insulated space of second evaporator; the control logic circuit compares the outdoor temperature and the temperature within the insulated space associated with second evaporator, when the temperature measured by second temperature sensor is higher than the outdoor temperature, second venting fan will run slowly or stop running to prevent the heat from escaping into the open air through cold-air-exit duct. During the defrosting process of the second evaporator, first evaporator continues to operate to absorb heat from the ambient air flow so that main condenser can maintain the temperature within the indoor space; During the second stage defrosting of each evaporator, each indoor-air-intake fan is drawing the indoor air into its associated evaporator, and the outdoor air is drawing into the indoor space through other ventilation duct for ventilation purpose, or an indoor ventilation fan can co-work with this system and draws outdoor air into the indoor area during the second stage defrosting of each evaporator.
 6. A cross anti-freeze-fluid-defrosting heat pump system comprising: a) Main compressor for pumping and pressurizing the refrigerant into main condenser, b) Refrigerant-to-fluid heat exchanger for transferring the heat energy into the anti-freeze fluid flow circulation, c) First anti-freeze-fluid-defrost evaporator consisting of one refrigerant flow passage and one anti-freeze-fluid passage, d) Second anti-freeze-fluid-defrost evaporator consisting of one refrigerant flow passage and one anti-freeze-fluid passage, e) One expansion valve for regulating the refrigerant pressure drop between main condenser and the refrigerant flow passage of both said anti-freeze-fluid-defrost evaporators, f) First control valve for controlling the refrigerant flow in the refrigerant flow passage of first anti-freeze-fluid-defrost evaporator, g) Second control valve for controlling the refrigerant flow in the refrigerant flow passage of second anti-freeze-fluid-defrost evaporator, h) First fluid pump for controlling and generating the anti-freeze fluid flow through the anti-freeze fluid passage of first anti-freeze-fluid-defrost evaporator, i) Second fluid pump for controlling and generating the anti-freeze fluid flow through the anti-freeze fluid passage of second anti-freeze-fluid-defrost evaporator, j) First venting fan for controlling the air flow through the separated space of first anti-freeze-fluid-defrost evaporator, k) Second venting fan for controlling the air flow through the separated space of second anti-freeze-fluid-defrost evaporator, j) the logic control circuit and the environment temperature sensor for detecting the frost condition and controlling the defrosting process; When the system is working under the environment temperature that does not require defrosting, first fluid pump and second fluid pump are not operating so that refrigerant-to-fluid heat exchanger does not dissipate any heat energy, the refrigerant is pressurized in main compressor and flows through main condenser to release heat, then the refrigerant flows through expansion valve into first anti-freeze-fluid-defrost evaporator and second anti-freeze-fluid-defrost evaporator, then the refrigerant is evaporated and drawn back to compressor; When first anti-freeze-fluid-defrost evaporator is defrosting with the first stage defrosting method, first control valve is closed to stop refrigerant flow in first anti-freeze-fluid-defrost evaporator, and then first venting fan is running at full capacity to defrost first evaporator with the ambient air flow; When second anti-freeze-fluid-defrost evaporator is defrosting with the first stage defrosting method, second control valve is closed to stop refrigerant flow in second anti-freeze-fluid-defrost evaporator, and then second venting fan is running at full capacity to defrost second anti-freeze-fluid-defrost evaporator with the ambient air flow; When first anti-freeze-fluid-defrost evaporator is defrosting with the second stage defrosting method, first control valve is closed to stop refrigerant flow in first anti-freeze-fluid-defrost evaporator, first fluid pump is pumping to generate the anti-freeze fluid flow which transfers the heat from refrigerant-to-fluid heat exchanger to first anti-freeze-fluid-defrost evaporator, therefore, the system can defrost with the heat energy generated from main compressor and the heat energy absorbed by the other operating anti-freeze-fluid-defrost evaporator; first venting fan decreases speed or stops running to prevent heat from escaping out of the separated space of first anti-freeze-fluid-defrost evaporator; When second anti-freeze-fluid-defrost evaporator is defrosting with the second stage defrosting method, second control valve is closed to stop refrigerant flow in second anti-freeze-fluid-defrost evaporator, second fluid pump is pumping to generate the anti-freeze fluid flow which transfers the heat from refrigerant-to-fluid heat exchanger to second anti-freeze-fluid-defrost evaporator, therefore, the system can defrost with the heat energy generated from main compressor and the heat energy absorbed by the other operating anti-freeze-fluid-defrost evaporator, second venting fan decreases speed or stops running to prevent heat from escaping out of the separated space of second anti-freeze-fluid-defrost evaporator; During the second stage defrosting, each defrosting anti-freeze-fluid-defrost evaporator is heated up by the heat energy absorbed by the functioning anti-freeze-fluid-defrost evaporator and the heat energy generated by main compressor.
 7. A cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 5, wherein the control logic further comprises a forced-ventilation operation control method, wherein each indoor-air-intake control valve is open and its associated indoor-air-intake fan is running to draw in the indoor air for ventilation purpose during the operation of its associated evaporator; under this operation mode, the outdoor air flow is mixed with the indoor air flow through each indoor-air-intake control valve; by controlling the temperature of this mixed air flow, the time required for each defrosting process can be greatly reduced, or under some conditions, the system can continue to operate without defrosting; in the case when the outdoor temperature is between 5 to 12 degree Celsius, the temperature of the mixed air flow can be raised to 12 degree so that the system can greatly increase the operation time of both first evaporator and second evaporator before the first stage defrosting is required; if the temperature of the mixed air flow is raised to above 12 degree, the system can operate without defrosting. If the outdoor temperature is below 5 degree, raising the temperature of the mixed air flow can also greatly increase the operation time of both first evaporator and second evaporator before the second stage defrosting is required; the temperature of the mixed air flow can be controlled by each indoor-air-intake control valve, the operation speed of each venting fan and indoor-air-intake fan; under this operation mode, the venting fans are operating at the speed based on the ventilation rate required or the temperature of the mixed air flow required.
 8. A cross reverses defrosting heat pump system as defined in claim 1, wherein each reverse-flow control valve and its associated upper-flow control valve can be substituted with a rotary upper-flow control valve capable of same functions; each lower-flow control valve and its associated one-way valve can be substituted with a rotary lower-flow control valve capable of same functions.
 9. A cross reverses defrosting heat pump system as defined in claim 1 further comprising: a) a pressure-boost jet pump connecting its input side from the refrigerant outlet of said main compressor and its output side to the inlet of said main compressor, b) a pressure-boost control valve for controlling the amount of the refrigerant flow through said pressure-boost jet pump; The pressure-boost jet pump utilizes the high refrigerant pressure from the outlet of said main compressor to adjust the intake refrigerant pressure of the said main compressor for optimum load.
 10. A cross reverses defrosting heat pump system as defined in claim 9, wherein the said pressure-boost jet pump can be other mechanical turbo intake devices or a rotary pump.
 11. A cross defrosting heat pump system as defined in claim 2 further comprising: a) a pressure-boost jet pump connecting its input side from the refrigerant outlet of said main compressor and its output side to the inlet of said main compressor, b) a pressure-boost control valve for controlling the amount of the refrigerant flow through said pressure-boost jet pump; The pressure-boost jet pump utilizes the high refrigerant pressure from the outlet of said main compressor to adjust the intake refrigerant pressure of the said main compressor for optimum load.
 12. A cross reverses defrosting heat pump system as defined in claim 11, wherein the said pressure-boost jet pump can be other mechanical turbo intake devices or a rotary pump.
 13. A cross defrosting heat pump with separate refrigerant circulation as defined in claim 3 further comprising: a) a pressure-boost jet pump connecting its input side from the refrigerant outlet of each compressor and its output side to the inlet of each compressor, b) a pressure-boost control valve for controlling the amount of the refrigerant flow through said pressure-boost jet pump; The pressure-boost jet pump utilizes the high refrigerant pressure from the outlet of each compressor to adjust the intake refrigerant pressure of each compressor for optimum load.
 14. A cross defrosting heat pump with separate refrigerant circulation claim 13, wherein the said pressure-boost jet pump can be other mechanical turbo intake devices or a rotary pump.
 15. A cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 5 further comprising: a) one pressure-boost jet pump connecting its input side from the refrigerant outlet of said main compressor and its output side to the inlet of said main compressor, b) a pressure-boost control valve for controlling the amount of the refrigerant flow through said pressure-boost jet pump; The pressure-boost jet pump utilizes the high refrigerant pressure from the outlet of said main compressor to adjust the intake refrigerant pressure of said main compressor for optimum load.
 16. A cross defrosting heat pump with separate refrigerant circulation as defined in claim 5, wherein the said pressure-boost jet pump can be other mechanical turbo intake devices or a rotary pump.
 17. A cross anti-freeze-fluid-defrosting heat pump system as defined in claim 6 further comprising: a) one pressure-boost jet pump connecting its input side from the refrigerant outlet of said main compressor and its output side to the inlet of said main compressor, b) a pressure-boost control valve for controlling the amount of the refrigerant flow through said pressure-boost jet pump; The pressure-boost jet pump utilizes the high refrigerant pressure from the outlet of said main compressor to adjust the intake refrigerant pressure of said main compressor for optimum load.
 18. A cross anti-freeze-fluid-defrosting heat pump system as defined in claim 17, wherein the said pressure-boost jet pump can be other mechanical turbo intake devices or a rotary pump.
 19. A cross reverses defrosting heat pump system as defined in claim 1 further comprising: at least one additional set of evaporator and the control valves required for cross reverse defrosting; when a evaporator is defrosting with the second stage defrosting method, all other operating evaporators continues to absorb heat from the environment to provide the energy for heating and defrosting purpose.
 20. A cross defrosting heat pump system as defined in claim 2 further comprising: at least one additional set of evaporator and defrost condenser and the control valves required for cross defrosting; when a evaporator is defrosting with the second stage defrosting method, all other operating evaporators continues to absorb heat from the environment to provide the energy for heating and defrosting purpose.
 21. A cross anti-freeze-fluid-defrosting heat pump system as defined in claim 6 further comprising: at least one additional set of anti-freeze-fluid-defrost evaporator and the control valves required for anti-freeze-fluid defrosting method, when an anti-freeze-fluid-defrost evaporator is defrosting, all other operating evaporators continue heating and provide the heat energy to defrost that defrosting anti-freeze-fluid-defrost evaporator with the anti-freeze-fluid flow through said refrigerant-to-fluid heat exchanger.
 22. A cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 5 can further combine the cross reverse defrosting heat pump as defined in claim 1 to increase the efficiency of the second stage defrosting method; when the system is defrosting with the second stage defrosting method, the defrosting evaporator is defrosting with the indoor air flow and the hot refrigerant flow directly from said main compressor.
 23. A cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 5 can further combine with the cross defrosting heat pump as defined in claim 2 to increase the efficiency of the second stage defrosting method; when the system is defrosting with the second stage defrosting method, the defrosting evaporator is defrosting with the indoor air flow and the heat dissipated from its associated defrost condenser.
 24. A cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 5 can further combine with the cross anti-freeze-fluid-defrosting heat pump system as defined in claim 6 to increase the efficiency of the second stage defrosting method; when the system is defrosting the second stage defrosting method, the defrosting anti-freeze-fluid-defrost evaporator is defrosting with the indoor air flow and said anti-freeze-fluid flow.
 25. A cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 5 can further combine with the cross defrosting heat pump with separate refrigerant circulation as defined in claim 3 to increase the efficiency of the second stage defrosting method; when the system is defrosting with the second stage defrosting method, the defrosting evaporator is defrosting with the indoor air flow and the heat dissipated from its associated defrost condenser in contact.
 26. The cross reverse defrosting heat pump system as defined in claim 1, and the cross defrosting heat pump system as defined in claim 2, and the cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 6, and the cross defrosting heat pump with separate refrigerant circulation as defined in claim 3, and the cross anti-freeze-fluid-defrosting heat pump system as defined in claim 6 comprises a control logic which employs the first stage defrosting method under the environment temperature ranged from 12 degree to 5 degree Celsius.
 27. The cross reverse defrosting heat pump system as defined in claim 1, and the cross defrosting heat pump system as defined in claim 2, and the cross defrosting heat pump with self-ventilation and humidity control system as defined in claim 6, and the cross defrosting heat pump with separate refrigerant circulation as defined in claim 3, and the cross anti-freeze-fluid-defrosting heat pump system as defined in claim 6 comprises a control logic which employs the second stage defrosting method under the environment temperature of 5 degree Celsius and lower. 